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Dear PETSc group, I'm reading the DS part for the discretization start from SNES ex17. c which is a demo for solving linear elasticity problem. I have two questions for the details. The first question is for the residual function. Is the residual
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Dear PETSc group,</div>
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I'm reading the DS part for the discretization start from SNES ex17.c which is a demo for solving linear elasticity problem. I have two questions for the details.</div>
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The first question is for the residual function. Is the residual calculated as this? The dot product is a little weird because of the dimension of the result.</div>
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<img size="34587" contenttype="image/png" style="max-width: 1598px;" data-outlook-trace="F:1|T:1" src="cid:b790e49a-5adb-4085-807c-546e7c2d941f"></div>
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Here \sigma is the stress tensor, \phi_i is the test function for the i-th function (Linear elasticity in 3D contains three equations).</div>
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The second question is how to derive the Jacobian of the system (line 330 in ex17.c). As shown in the PetscDSSetJacobian, we need to provide function g3() which I think is a 4th-order tensor with size 3*3*3*3 in this linear elasticity case. I'm not sure how
to get it. Are there any references on how to get this Jacobian?</div>
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<span style="font-size: 12pt; color: rgb(0, 0, 0);">I've checked about the comment before this Jacobian function (</span><span style="font-size: 16px; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">line 330 in ex17.c</span><span style="font-size: 12pt; color: rgb(0, 0, 0);">)
but don't know how to get this.</span></div>
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Thanks in advance!</div>
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Best Regards,</div>
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Yujie</div>
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